ORIGIN OF LIFE UPON THE EARTH 187
pToyed to be of the utmost importance in the life processes in that recog- nized in the early part of the nineteenth century and denoted by the term catalysis, first applied by Berzelius in 1835. A catalyzer is a sub- stance which modifies the velocity of a distant chemical reaction without itself being used up by the reaction. Thus chemical reactions may be accelerated or retarded and yet the catalyzer loses none of its energy. In a few eases it has been definitely ascertained that the catalytic agent does itself experience a series of changes. The theory is that catalytic phenomena depend upon the alternate decomposition and recomposition, or the alternate attachment and detachment of the catalytic agent.
DiscoTered as a property in the inorganic world catalysis has proved to underlie the great series of functions in the organic world which may be comprised in the physical term interaction. The researches of Ehr- lich and others fully justify Huxley's prediction of 1881 that through therapeutics it would become possible ^' to introduce into the economy a molecular mechanism which, like a cunningly contrived torpedo, shall find its way to some particular group of living elements and cause an explosion among them, leaving the rest untouched.^' In fact, the interacting agents known as " enzymes are such living catalyzers"* which accelerate or retard reactions in the body by forming intermediary unstable compounds which are rapidly decomposed, leaving the cata- lyzer (*. e.j enzyme) free to repeat the action. Thus a small quantity of an enzyme can decompose indefinite quantities of a compound. The activity of enzymes is rather in the nature of the "interaction" of Newton than of direct action and reaction, because the results are pro- duced at a distance and the energy liberated may be entirely out of pro- portion to the internal energy of the catalyzer. The enzymes being themselves complex organic compounds act specifically because they do not affect alike the different organic compounds which they encounter in the fluid circulation.
Hence, as a fifth hypothesis relating to the origin of organisms, we may advance the idea that the evolution and specialization of various catalyzers (including enzymes or "unformed ferments") has proceeded step by step with the evolution of plant and animal functions. In the evolution from the single-celled to the many-celled forms of life and the multiplication of these cells into hundreds of millions, into billions, and into trillions, as in the larger plants and animals, biochemical coordi- nation and correlation become increasingly essential. In fact, none of the discoveries we have hitherto described throws greater illumination on the life processes than this connected with the internal secretions and the by-products of metabolism in the circulation of the plant and animal fluids. It is known that, as Huxley prophesied, enzymes do reach par- ticular groups of living elements and leave others tmtouched. For ex- ample, the enzyme developed in the yeast ferment produces a different
U9 Loeb, Jaeqnes, 1906, pp. 26, 28.
�� �
